Photographic copiers of today are equipped almost exclusively with a so-called scanner which allows the picture by picture photoelectric scanning of the images on a film to be copied with a more or less high resolution, whereby different optical arrangements are used. The digital electric scanning signals produced by the scanner which represent the picture information are in classical optical copiers (printers) analysed for exposure control or correction. In modern, so-called digital copiers, the scanning signals are used after suitable processing for the control of a digital print-producing arrangement, for example, a colour printer or a digital exposure arrangement. A satisfactory picture quality can thereby naturally only be achieved with relatively high resolution scanners and print-producing arrangements.
A high resolution photoelectric scanning also requires a high mechanical precision of the scanning device. In order to avoid positioning errors during the scanning of a film, the film must be very exactly guided at least in the region of the scanning site. This is only possible if the guide elements provided therefor in the scanning device are exactly adjusted to the dimensions (width) of the film. Upon change of the film format, the guide elements must be correspondingly re-adjusted, which means either a separate scanning arrangement must be provided for each film format, or the scanning arrangement must be correspondingly refitted upon each change of the film format. However, this would be very cumbersome, since in the practical application, especially with a mini lab, frequently changing film formats must be expected.